Utilization of By-Products from the Tequila Industry

Tequila production and export are at an all-time high, determining a strong increase in agave utilization for tequila production and, in turn, waste generation. Existing data underscores the presence of a substantial waste volume that currently lacks widespread utilization, but that holds biotechnological potential for generating various products.

Leaves, bagasse, and vinasse constitute the primary by-products derived from agave industry activities. Leaves constitute about 70-80% of the agave plant, and every liter of tequila produced at 55% Alc/Vol generates ~1.4 kg of bagasse (at 60% humidity) and 10 lt of vinasse.

• Agave leaves (called pencas), are the tall fibrous stem of the agave plant. The main environmental problems is linked to the fact that they are generally entirely discarded at cutting sites, where they cannot be consumed directly by livestock and obstruct the growth of herbaceous plants in the pasture

• Bagasse is the residual fiber remaining after extraction and fermentation stages of tequila making. It mainly consists of lignocellulosic material and it is generally discarded on soil or crop fields or applied improperly on agricultural land. Its uncontrolled decomposing process produces toxic liquids that cause pollution in soil and bodies of water and compromises soil fertility.

• Vinasse is the liquid residue obtained after distillation, it has high concentration of organic material in suspension (on average, composed of 90% water and 10% solids) and a low pH. The main environmental problem is linked to the fact that when discharged without treatment into water bodies or crop fields causes contamination and destroyes soil productivity. If used for irrigation, components such as fats and oils form a film capable of waterproofing soils, preventing water filtration. Also has negative effect on microbiota and soil texture. If released at elevated temperatures (85 - 90 °C) into compost production mixtures, generates a thermal pollutant that breaks the composting cycle.

Those by-products offer versatile applications that classified into eight overarching domains: animal feed, paper and textiles, biobased materials and composites, construction materials, functional ingredients and prebiotics, waste-to-energy generation, biofertilizer and water treatment technologies.

• Livestock feed: Agave Leaves can be repurposed to produce nutritious livestock feed and reduce soil stress. Shredded and fermented in closed containers for ~ 30 days, agave leaves produce a highly nutritious animal feed. This solution has a cost-effective and limited transport footprint, it reduces pressure to overgraze and enhancement of soil health and water retention and it leads to reduced emissions (use of waste and strong potential for carbon sequestration from agave plants).
  

• Fibers in animal and pet food: By-products of agri-food processing can be converted to animal feed & pet food using insect biotechnology (typically with BSF - Black Soldier Flies). Bioconversion is an efficient solution to produce feed functional ingredients, with low environmental impact. A further byproduct of this innovation is organic compost and fertilizer materials.

• Compost and fertilizer: Nutrients extracted from the agave crops can be processed into biofertilizers and composts and reintroduced into the same crops, leading to a sustainable and efficient nutrient cycle. In this process, A mixture of agave bagasse, leaves and settled biosolids from the distillation residues are watered with vinasse. Ashes can possibily be addded, post-evaluation, to the mix. This mixture is left for an average of 6 to 7 months for degradation.

• Biobased materials and composites: Agave by-products find application in the creation of bioplastics or as strengthening agents in polymer-based composite materials. The most used material is bagasse, and leaves and vinasse incorporation in composites and bioplastics improves specific thermal and mechanical characteristics. Those byproducts can also be used for the built environment, without polymers addition, to create adobe bricks and pressed boards. In the mix, vinasse increases water-proofness of the material and to replace potable water in production. The material created has cooling properties and low foorprint.

• Paper and textile: Leaves and bagasse fibers have multiple uses in various industries. Cellulose can be used for paper, yarns, textile, labels, stuffing for furniture and mattresses, etc. However, those projects are generally carried o non very small scale.

• Functional ingredients and prebiotics: Agave is a carrier of prebiotics with application in the food and pharmaceutical industry. Especially inulin from blue agave is commercialized as a sugar alternative.

• Waste to energy: Agave waste is a valuable biofuel and biogas feedstock, supporting in renewable energy production and reducing waste disposal challenges. Agave bagasse is used to produce bioethanol though fermentation and briquettes thought a drying and compression process. Vinasse and bagasse, also as a byproduct of fermentation to produce ethanol, are used to generate hydrogen via dark fermentation and methane via anaerobic digestion. Studies show how bioethanol yields from agave bagasse rival or surpass other ethanol sources like corn, switchgrass, and sugarcane in terms of energy, water use, and greenhouse gas balance.

• Water treatment: Residual bagasse is being investigated as a method to clean polluted water, soil, and air. However, the technology is not ready yet for commercial application.